The present invention generally relates to vent apparatus for fuel-fired direct vent heating appliances and, in a preferred embodiment thereof, more particularly relates to a specially designed snap-together concentric direct vent structure section for such appliances, and methods fabricating the vent structure section.
Gas fired heating appliances, such as furnaces, located in interior paces of buildings require during their firing a continuous supply of combustion air. At the same time, such appliances generate hot combustion gases which must be appropriately discharged therefrom to the exterior of the building. One technique for supplying combustion air to a fuel-fired heating appliance, while at the same time creating a path through which its generated combustion gases may be discharged to the exterior of the building, is to operatively connect a concentric direct vent structure to the appliance.
As conventionally constructed, a direct vent structure of this general type is defined by lengths of concentric inner and outer ducts extended between the furnace and a combination intake/discharge assembly mounted on the outer side of an exterior wall of the building. The concentric inner and outer ducts define therebetween an annular space, with combustion gases from the furnace being discharged through the interior of the inner duct and out the intake/discharge assembly, while outside combustion air is drawn inwardly through the intake/discharge assembly and through the inner duct/outer duct annulus to the furnace.
To maintain the inner and outer ducts in a concentric alignment, stand-off structures are secured within the outer duct, extend through the inner duct/outer duct annulus, and provide lateral centering support for the inner duct. The overall concentric direct vent structure is typically made up from axial sections of concentric inner duct/outer duct assemblies which are appropriately connected in end-to-end relationships to form the desired length of the finished direct vent structure. From a materials standpoint, each of these sections conventionally includes an aluminum inner duct, a galvanized steel outer duct, and one or more non-galvanized steel stand-off members secured within the outer duct and supporting the inner duct therein.
Various well-known problems, limitations and disadvantages have heretofore been associated with the conventional manufacture and assembly of the individual longitudinal sections of this general type of concentric direct vent structure. For example, the installation of the stand-off structures within the outer duct tends to be difficult and relatively expensive. Additionally, the connection of the stand-off structures to the inner duct also tends to be difficult and relatively expensive. Typically, this connection of the stand-off structures to the inner duct undesirably required penetration of the inner duct (for example, with rivets), and thus resulting gas leaks in the inner duct, since spot welding techniques could not be used to join the aluminum inner duct to the steel stand-off structures. Moreover, the proper insertion and positioning of the inner duct section within its associated outer duct section tends to be a tedious and time-consuming task, which undesirably adds to the overall fabrication cost of conventionally constructed concentric direct vent assemblies of this general type.
From the foregoing it can be seen that a need exists for improvements in the manner in which a longitudinal section of a concentric duct direct vent structure is constructed. It is to this need that the present invention is directed.